V2024.05.0 release fixes

[arnopo]

Issues were detected in Zephyr during CI when integrating the new release v2024.05.0:

[24/182] Building C object zephyr/CMakeFiles/zephyr.dir/lib/open-amp/resource_table.c.obj
In file included from /zephyrproject/zephyr/lib/open-amp/./resource_table.h:11,
                 from /zephyrproject/zephyr/lib/open-amp/resource_table.c:30:
/zephyrproject/modules/lib/open-amp/open-amp/lib/include/openamp/virtio.h:83:2: warning: #warning "VIRTIO_DRIVER_SUPPORT and/or VIRTIO_DEVICE_SUPPORT should be defined" [-Wcpp]
   83 | #warning "VIRTIO_DRIVER_SUPPORT and/or VIRTIO_DEVICE_SUPPORT should be defined"
      |  ^~~~~~~
[26/182] Building C object CMakeFiles/app.dir/src/main_remote.c.obj
In file included from /zephyrproject/modules/lib/open-amp/open-amp/lib/include/openamp/rpmsg_virtio.h:19,
                 from /zephyrproject/modules/lib/open-amp/open-amp/lib/include/openamp/open_amp.h:12,
                 from /zephyrproject/zephyr/samples/subsys/ipc/openamp_rsc_table/src/main_remote.c:16:
/zephyrproject/modules/lib/open-amp/open-amp/lib/include/openamp/virtio.h:83:2: warning: #warning "VIRTIO_DRIVER_SUPPORT and/or VIRTIO_DEVICE_SUPPORT should be defined" [-Wcpp]
   83 | #warning "VIRTIO_DRIVER_SUPPORT and/or VIRTIO_DEVICE_SUPPORT should be defined"
      |  ^~~~~~~

The root cause is that the application can include thevirtio.hheader without defining VIRTIO_DRIVER_SUPPORT or VIRTIO_DEVICE_SUPPORT, which should not result in a warning or error.

This pull request:

• Fixes the warning message.
• Defines the VIRTIO_ROLE_IS_DEVICE and VIRTIO_ROLE_IS_DRIVER macros based on the definitions of VIRTIO_DEVICE_SUPPORT and VIRTIO_DRIVER_SUPPORT.

Fix also unreferenced endpoint->privfield, found in Zephyr and introduced in
https://github.com/OpenAMP/open-amp/commit/9905d67bd96016b62f37b7031ba0723c7b905570

[arnopo]

New issue found in Zephyr introduced in
https://github.com/OpenAMP/open-amp/commit/9905d67bd96016b62f37b7031ba0723c7b905570

[arnopo]

Minor fix on coommit message subject to add "lib:" prefix